WASHINGTON (MarketWatch) — The full scope of Hillary Clinton’s loss and Donald Trump’s victory will become apparent this week as the newly elected Congress convenes.

We all know the Republicans swept the elections, winning the White House and retaining control of both houses of Congress.

But it is where these victories came from and how they were made that tells us what will happen in the two years this 115th Congress will have until midterm elections in 2018.

There is obviously a great deal of overlap between Trump’s campaign pledges and the standing agenda of congressional Republicans under House Speaker Paul Ryan and Senate Majority Leader Mitch McConnell.

But there are also some significant differences — in the approach to trade issues and deficit spending, to name just two. Trump’s pledge to maintain and defend Medicare and Social Security is another important difference.

Congressional Republicans may think they are about to reach the Promised Land, and Washington Post reporter David Weigel this week neatly summed up the various bills they have vetted on issues from deregulation to repealing Obamacare that are just waiting for a president to sign into law.

But if Trump has proven anything in his idiosyncratic campaign, it is that he is hardly just “a Republican with enough working digits to handle a pen” — the ideal president once dreamed of by tax reform activist Grover Norquist.

In other words, it’s not likely Trump will simply rubber-stamp legislation that a Republican Congress churns out.

Why would someone who trumpets his expertise in negotiation simply give Congress what it wants? He will hold back on those signatures as leverage to get what he wants, especially when it runs counter to or simply beyond the lawmakers’ agenda.

Salena Zito, a pro-Trump commentator who catapulted to prominence for her insights into the Trump campaign, reminds us that the key to understanding the incoming president is his 1987 book, “The Art of the Deal.”

Trump voters understood what mainstream media commentators still haven’t grasped — many of his statements are not ex cathedra pronouncements on policies but negotiating ploys. And, yes, many of them are not completely true.

“Throughout the book, he is always negotiating, no matter if he was coming from a full truth or not, didn’t matter,” Zito writes of the 1987 book in the Washington Examiner. “It is always about the value of what is at stake. In that type of barter, truthfulness becomes irrelevant, it only has actuality if the deal is struck and the facts come out.”

Which brings us back to Congress and how Trump will deal with it.

Even though Republicans retained control of both houses, Democrats trimmed those majorities even as Clinton won a commanding plurality in the popular vote for president. The Republican majority in the Senate went to 52 from 54, out of 100, and to 241 from 247, out of 435 in the House.

The electoral upsets that enabled Republicans to maintain the Senate majority were the victories of Ron Johnson in Wisconsin and Pat Toomey in Pennsylvania, two Republican incumbents most pollsters predicted would lose to Democratic challengers, Russ Feingold and Kathleen McGinty.

But Trump’s surprising win in those swing states also lifted the two incumbents to an unexpected victory. Had Clinton’s campaign in those states been slightly more effective she might be the president-elect with Democratic control of the Senate.

Democrats were bound to recapture the Senate seat in Illinois, but they also won a closely fought battle in New Hampshire, where the popular governor, Maggie Hassan, defeated Republican incumbent Kelly Ayotte. It may well have been Ayotte’s disavowal of Trump that cost her the margin of victory.

The lesson here, as with unsuccessful Nevada Senate candidate Joe Heck, who lost ground after distancing himself from Trump, is that Republican lawmakers need Trump’s support to gain voter favor more than he needs them.

The picture from the House results is a little less clear-cut. Although every member is up for re-election every two years, the rate of incumbency victories is very high. In 2016, 380 of the 393 incumbents seeking re-election won, for an incumbency rate of 96.7%.

According to Ballotpedia, Democrats tend to gain seats in presidential election years with their higher voter turnout, while Republicans tend to gain in the midterm elections.

For instance, Democrats gained eight sets in 2012 and 24 in 2008, which make the net gain of six in 2016 seem relatively small.

So Republicans are likely to make gains in the House in 2018. In the Senate, Republicans will be defending only eight seats, while Democrats will be defending 25 — 10 of which are in states that Trump won.

Those 10 Democratic senators will be very careful about thwarting Trump, which makes his leverage in the Senate considerably larger than the 52 Republicans.

Trump may be a political novice, but if he’s half as skillful at negotiation as he claims to be, he will quickly grasp how to play the legislature like a fiddle.

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